Justin Bieber has topped the charts again — for being one of the worst hosts of “Saturday Night Live.”

“I really didn’t enjoy having Justin Bieber around,” former cast member Bill ­Hader says in the new edition of “Live From New York: An Uncensored History Of Saturday Night Live,” written by James Andrew Miller and Tom Shales.

“He’s the only one who lived up to the reputation. I think that’s the only time I felt that way in eight years.”

Backstage machinations, the love-hate relationship SNL staffers have with producer Lorne Michaels, the birth of classic bits — all are hashed out in the book by the show’s latest generation of writers and cast members.

Among this generation’s high points was the night Fred Armisen first impersonated then-New York Gov. ­David Paterson, who is legally blind. Armisen-as-Paterson was dropping by the Weekend Update desk to talk about taking over from disgraced former Gov. Eliot Spitzer.

Kenan Thompson spoofed Rev. Al Sharpton on Saturday Night Live.

“Fred slid out to the Update desk from offstage,” says sketch co-writer John Mulaney — and then kept going, right past anchor Seth Meyers.

“Everyone laughed so goddamn hard,” Mulaney says. “We wrote [Paterson] like a comedian who burned everyone else, especially New Jersey. Though we didn’t want to offend anybody, it was kind of interesting to have The New York Times saying, ‘To call this humor sophomoric would be an insult to sophomores,’ and I was just like, ‘Oh, my God, how New York Times-ey.’ ”

When Kenan Thompson impersonated the Rev. Al Sharpton, the activist was both flattered and insulted.

“I’ve been parodied more than most, but I think of it as a compliment,” Sharpton says in the book. “I just wish Kenan would lose some weight before he does me. I’m not that fat anymore. Kenan needs to take off about 50 pounds to play me.”

This latest group of writers and cast members — which included Hader, Armisen, Myers, Tina Fey, Amy Poehler, Jimmy Fallon and Kristen Wiig — were, for the most part, far more mature and health-conscious than their ’70s forebears.

Fred Armisen playing then-Gov. David Paterson on SNL.

“You have these hosts who come in and go, ‘Hey, I’m on SNL, let’s party!’ ” Hader says. “And we were like, ‘Oh, I’m not eating sugar.’ ”

The one thing that has remained a constant through the show’s 39 seasons is Michaels’ enigmatic approach to everything — from hiring and firing people to running the show to cultivating or terminating friendships. Even Gwyneth Paltrow confesses to being intimidated by him.

“I’d never met such a WASP-y seeming Jew in my life,” she says. “And I was like, where’s the ‘in,’ you know?”